Processes

The investment casting process begins with the production of wax replicas of the desired castings. These replicas, called patterns, are injection moulded in metal dies. A number of patterns are attached to a wax stem / runner bar to form a cluster / tree. After cleaning, the trees are immersed into a ceramic slurry and then covered with a  fine fire resistant stucco. After a couple of layers, the shell is allowed to dry. When the shell is completely dry, the wax is melted out in a high pressure steam autoclave, leaving a hollow void within the mould, which exactly matches the shape of the assembly.

Prior to casting, the shells are fired in an oven that burns out any remaining wax residue. The molten metal is cast into the hot shell. The shell is allowed to cool and the ceramic shell is broken off and the parts are cut off from the runner bar. The castings are shot blasted with high pressure sand and water and then the casting are cleaned and in-gates removed by a grinding process. The castings then runs past a rigorous quality check and then stored for dispatch.
All of the above in short boils down to: A die which is the negative of the casting which produces a positive pattern. A Ceramic mould which is formed around the wax  pattern and when dewaxed leaves a cavity which creates the positive casting when cast.